Club 80-90 Forums

Hi all, i had a compression test and i have low compression on two cylinders on my 2.0 cu Aircooled engine. I am going to take the engine out today for further inspection. I need advice on what the main cause is for low compression. i will be removing the heads to see what the problem is but its a first for me and any advice will be good i will be looking at the valves and piston and barrels for damage. Wish me luck

ringwear is the usual suspect..along with valve seat wear.
There is a test to determine which one.
Because you're asking the question I'm guessing the test was not done at the garage.
presumably they thought it might not be usefull as a wet compression test on a flat four is not as accurate as an upright engine.

kevtherev wrote:ringwear is the usual suspect..along with valve seat wear.
There is a test to determine which one.
Because you're asking the question I'm guessing the test was not done at the garage.
presumably they thought it might not be usefull as a wet compression test on a flat four is not as accurate as an upright engine.

Cheers Kev, a friend of mine tested it at his garage and pots 1 and 2 were low on compression, i have just got the engine out (2 hrs work )
I will be taking the heads of for a closer inspection

Hello,

Aircooled stuff...

Head overhaul.. if they haven't been touched for years..

You will be looking at fitting new valve guides and valves..

Regrinding the valve seats..

and so on..

Watch out for 'blow' marks where the decompression rings have failed..



letting the compression go..



There must not be excessive play of the valves in the guides..



If the pistons and barrels are in good condition, then deglaze and fit new rings..

This thread may help:

https://club8090.co.uk/forum/viewtopic.php?f=37&t=118051" onclick="window.open(this.href);return false;

I shall be tuning and finishing this one soon...

If you are unsure.. you can always send them in the post to me..

Pm me if interested..

Aircooled bliss

Cordialement

sarran1955 wrote:Hello,

Aircooled stuff...

Head overhaul.. if they haven't been touched for years..

You will be looking at fitting new valve guides and valves..

Regrinding the valve seats..

and so on..

Watch out for 'blow' marks where the decompression rings have failed..



letting the compression go..



There must not be excessive play of the valves in the guides..



If the pistons and barrels are in good condition, then deglaze and fit new rings..

This thread may help:

https://club8090.co.uk/forum/viewtopic.php?f=37&t=118051" onclick="window.open(this.href);return false;

I shall be tuning and finishing this one soon...

If you are unsure.. you can always send them in the post to me..

Pm me if interested..

Aircooled bliss

Cordialement

Thanks for the offer Sarran This is my first time at going inside the engine but doing it mysellf is the only way i am going to learn about fixing things. I will be removing the heads next week and ime sure i will be putting some pics up for you to give me some advice on If i realy get stuck then the heads will be in the post to you mate
Cheers for the pictures and advice
Brian.

do you have any tell tale signs of damage?

i had two low compression readings on my cu but also a 'james bond' style trail of white smoke behind me whenever i put my foot down, and tbh fairly poor performance to go with it. at the time wasnt sure whether she was a keeper so pulled the engine out (115k btw) and removed heads and barrels. visually inspected the heads, barrels and pistons. seemed ok (ish) apart from two pistons had broken rings on the offending cylinders. no really bad scores or anything so basically got a gasket set and new rings, re ringed all the pistons, and put it all back together with new gaskets, (didnt deglaze, only necessary if you rebore).

broke a couple of rings in the process so i have spares if you do the same and need any!!

have had two 3000+ mile trips to spain (murcia) since and she runs really well.

take your time and all should be fine.

ian

sooperspur wrote:do you have any tell tale signs of damage?

i had two low compression readings on my cu but also a 'james bond' style trail of white smoke behind me whenever i put my foot down, and tbh fairly poor performance to go with it. at the time wasnt sure whether she was a keeper so pulled the engine out (115k btw) and removed heads and barrels. visually inspected the heads, barrels and pistons. seemed ok (ish) apart from two pistons had broken rings on the offending cylinders. no really bad scores or anything so basically got a gasket set and new rings, re ringed all the pistons, and put it all back together with new gaskets, (didnt deglaze, only necessary if you rebore).

broke a couple of rings in the process so i have spares if you do the same and need any!!

have had two 3000+ mile trips to spain (murcia) since and she runs really well.

take your time and all should be fine.

ian

My problem started after the van was sitting on my drive for 1 year, when i took it for a drive it judders at any constant speed and the odd backfire so i took it in to my mate to get it looked at and the timeing set up. But when he tryed to set the timeing it was impossible to get even close. He then done the compression test and found low compression in pistons 1&2. When i was driveing back home it deceided to fire on just two cylinders for around a mile then cut back in. So the time has come to investigate further. I will post some pics up when i get the heads of for closer inspection.
Brian.

Well i have removed the enging and started pulling it appart for closer inspection. i have got one head off and i will be removing the other this morning :O)


It's a bit of an oily mess at the mo
I will post some pics up of the heads later today